柱塞主缸密封凹槽表面缺陷检测系统

Surface defect detection system for seal groove of plunger main cylinder

汽车柱塞主缸凹槽表面缺陷导致柱塞主缸密封性能不良,进而影响汽车制动性能。由于主缸口径小、半封闭,内侧凹槽缺陷难以检测,因此设计360°锥面镜对内侧凹槽360°全景成像,并由视觉传感器采集图像。二维伺服电机驱动系统实现锥面镜在缸体内的上下移动和主缸工件的自动旋转,完成锥面镜在主缸内侧4个凹槽的精确定位以及工件旋转角度的准确定位。系统配合NI Assistant图像处理技术,实现环状图片的矩形展开及自动拼接,经标定后采用投影变换、孤立点面积阈值处理以及对象长宽比阈值处理等图像处理方法实现缺陷检测。检测得到X、Y方向像素当量均小于0.1 mm,且准确识别砂眼、划痕等缺陷。该方法快速稳定,可提高工业检测效率。

The groove defect of the main cylinder of the automobile plunger is a major cause for the sealing performance of the main cylinder,which further affect the braking performance of the automobile.However,it is difficult to detect the inner groove flaw as the main cylinder caliber is small and semi-closed.Therefore,a 360°cone mirror is designed to present an omnidirectional imaging of the inner groove,and the image is acquired by the visual sensor.As for the two-dimensional servo motor drive system,the conical mirror can move up and down in the cylinder body and the main cylinder workpiece can automatically rotate,to finish the precise positioning of the four grooves in the inner side of the main cylinder and the accurate positioning of the workpiece rotation angle.When combining the system with the NI Assistant image processing technology,the annular image realizes rectangular stretch and automatic stitching.After calibration,the projection transformation,acnode area threshold processing,object aspect ratio threshold processing and other image processing methods are adopted for the defect detection.X and Y pixel equivalents are all less than 0.1 mm,and defects such as sand holes and scratches are accurately identified.The method is fast and stable,and improves the industrial testing efficiency.